server randomly died and prints only this error

[mokecode]

$soyTemplateRendererHelper.getRenderedTemplateHtml("com.atlassian.auiplugin:aui-experimental-soy-templates", "aui.page.header.soy", $templateParameters)

[Nic Brough -Adaptavist-]

There is not enough of the error to do any debugging here.  What are the lines below (the next 30 should be enough), and above (where we might need a hundred)?

The line you have there is not even an error, its just Confluence echoing out something it has been told to render, but not well enough for it to actually do it.  Tracking back that is important, but only if you think it is leading to a crash.